Heavy metal contamination poses serious threats to public health and ecosystems, with lead (Pb²⁺) being among the most hazardous owing to its persistence and toxicity. Rapid, cost-effective, and portable Pb²⁺ detection is therefore essential for environmental monitoring. In this study, rice husk-derived porous carbon (RHPC) was synthesized at three carbonization temperatures (350, 450, and 550 °C) and applied as a modifier for screen-printed electrodes (SPEs). RHPC suspensions were drop-cast on SPE surfaces and evaluated by square-wave anodic stripping voltammetry (SWASV). Structural characterization revealed increased porosity, higher surface area, and enhanced conductivity with rising carbonization temperature, with RHPC-550 showing the most favorable properties. Electrochemical measurements confirmed that RHPC-550-SPE achieved a markedly improved electrochemically active surface area (0.030 cm²) compared with the bare SPE (0.009 cm²). As a result, RHPC-550-SPE exhibited a higher sensitivity (0.037 µA/µg·L⁻¹), a lower detection limit (1.6 µg/L vs. 6.2 µg/L for bare SPE), and an excellent linearity (R² > 0.999) across 0–200 µg/L. Furthermore, negligible interference from common ions was observed, confirming reliable selectivity. These findings demonstrate that RHPC-modified SPEs provide a sustainable and low-cost sensing platform for trace Pb²⁺ monitoring in environmental applications.